# 通过 __iter__方法, 将迭代操作代理到容器中
class Node:
    def __init__(self,value):
        self._value = value
        self._children = []

    def __repr__(self):
        return 'Node({!r})'.format(self._value)

    def add_child(self,node):
        self._children.append(node)

    def __iter__(self): #通过此方法实现迭代器对象
        return iter(self._children)

if __name__ == '__main__':
    root = Node(0)
    child1 = Node(1)
    child2 = Node(2)
    root.add_child(child1)
    root.add_child(child2)
    for ch in root:
        print(ch)